1. Field of the Invention
The present invention relates to a shower unit and particularly, though not exclusively, to a shower unit in which the hot water is gas heated.
2. Discussion of the Background
Gas heated hot water offers a relatively inexpensive source of sanitary water for domestic consumption e.g. for showering, bathing, dishwashing and other applications requiring hot water.
In many gas heated hot water systems, the heated water is stored in a hot water storage tank (a so-called cylinder) before it is distributed in a piped system to a point or points of usage. At the point of usage for instance a hot water tap, the hot water is discharged into an open vessel such as a bath or sink. The amount of hot water discharged is regulated by the hot water tap, the maximum flow rate of the water through which being controlled by such parameters as the pressure difference between the cold water supply cistern and the tap and the flow resistance in the piping arising from frictional and throttling losses caused by sudden changes of flow area or flow direction.
Conventional gas heated hot water shower systems are similarly designed in the manner described above except that the shower outlet is supplied with both hot and cold water from a mixing chamber incorporating a mixing valve to regulate the temperature of the water delivered by the shower head. In this case the hot and cold water are supplied separately from the same initial source, namely a cold water supply cistern, some water being heated for storage as hot water in the cylinder before delivery to the mixing valve. Owing to the need for a mixing valve, the amount of hot water discharged at the shower head is limited by the flow restrictions at the mixing valve and at the shower head in which a number of relatively small openings are provided to produce the showering effect.
Customer satisfaction with any shower system appears mainly to depend upon the pressure of delivery of the water at the shower head. In the cases where the flow resistance in the system is relatively high the water pressure at the supply point of a gas heated hot water system (i.e. the cylinder outlet) may be insufficient to overcome the resistance at the shower head and this may lead to a situation where the water flow through the shower head is below the satisfactory level demanded by the customer.
This problem can be overcome by the insertion of an electrically powered shower booster pump between the shower head and the cylinder outlet. The booster pump raises the pressure head of the hot water supply to such a level that it can produce a powerful shower well beyond the pressure level provided by any gravity feed system.
Such booster pumps are relatively expensive and can make such gas heated shower systems economically unattractive to the average customer.
GB Patent Specification Nos. 1570484 (Anderson), 1581724 (Wilson) , and 2190022A (Pringle) all disclose shower units which are designed to obviate the need for a booster pump. In general these types of shower units comprise a mixing chamber of the type having one inlet for connection to a supply of hot water, another inlet for connection to a supply of cold water and a nozzle or jet connecting the cold water inlet to the chamber and adapted to cause the cold water to entrain the hot water to form at least a partial mixture for discharge from the chamber to a shower head or rose.
In use the cold water is supplied at mains pressure which is more than adequate to provide entrainment of the hot water and subsequent adequate delivery pressure from the shower head.
In these units the mixing chamber is connected to the shower head by means of a pipe, usually of a flexible kind, to permit the height of the shower head to be varied.
The provision of a pipe increases the overall cost of the unit and, moreover, tends to increase the length of the flow path from the nozzle to the shower head leading to an increase in frictional effects and a consequent reduction in the suction effect of the faster moving cold water jet on the slower moving hot water stream.